Magnetic Behavior of Pure Endohedral Metallofullerene Ho@C₈₂: A Comparison with Gd@C₈₂

Abstract

Magnetic properties of Ho@C82 and Gd@C82 were characterized in the temperature range of 1.8−100 K with an applied magnetic field up to 5 T. The isothermal magnetization curves of Gd@C82 and Ho@C82 follow the Brillouin function down to 8 and 12 K, respectively. Unlike Gd@C82, the fitting to the Curie−Wiess law for Ho@C82 results in an effective magnetic moment which is significantly smaller than that of a free Ho3+ ion. The magnetic moment reduction and the imperfect paramagnetic behavior of Ho@C82 are ascribed to the carbon cage crystal field effect, the partial hybridization of the orbitals of the entrapped Ho atom and the carbon cage, and the interactions between the metal centers.